Hall of Fame shooter, Pat Byrne cautioned me when I first started shooting Benchrest to NOT trust feel. A feeling of tightness is often caused by the base not being sized properly and is not the length of the cartridge from base to shoulder.
Shoulder bump and comparator readings
- Thread starter Alex Wheeler
- Start date
Hall of Fame shooter, Pat Byrne cautioned me when I first started shooting Benchrest to NOT trust feel. A feeling of tightness is often caused by the base not being sized properly and is not the length of the cartridge from base to shoulder.
tmwinds
Gold $$ Contributor
I agree, you can't determine shoulder bump by feel if the rest of the case doesn't fit. Shoulder bump is only one aspect of proper sizing.
Where is fguffey? He could explain this where none would understand.
Ledd Slinger
Silver $$ Contributor
This is exactly where the importance of spending the extra money to have custom built sizing dies comes into play
Are you saying Guffey thinks he’s too good for us, Lol!
Lone Hunter
Silver $$ Contributor
Yep, Because non of us can do what he does. He is the only one that can do anything right. The rest of us are dumbasses to him... The High Road.. Kinda Ironic don't you think..
nmkid
Gold $$ Contributor
Very true. Good input Alex.
I use the Innovative Technologies headspace gauge. The universal shoulder jaw can be adjusted to make contact on the shoulder of any case anywhere you desire and it only makes a very small amount of contact on the shoulder surface area. I always set it to contact right in the middle. The spring tension of the digital indicator arm always exerts the same amount of pressure on each case as well. Works very good for getting very accurate and repeatable readings on should bump measurements. I spin the case to find the lowest measurement. So repeatable that I can get the same reading on the same case removing and reinstalling it a hundred times.
Dont forget to deprime the cases before measuring!
View attachment 1105581
Man! I am a sucker for stuff like this! I was just getting ready to order some inserts for another tool. But, this looks like a new toy! Wouldn't have to look for inserts again.
Ledd Slinger
Silver $$ Contributor
Yeah it's nice because it's very fast and simple to adjust for different cases. Can use it to measure bullet seating depth on larger calibers as well. Adjust the jaw so it makes contact at the start of the ogive right at the lands touch point.
Only gripe is that the digital indicator doesn't have an auto shutoff and it takes weird little batteries. Sucks to replace them if you forget to turn it off cuz you have to do some searching to find them. Can get them on ebay or Amazon tho.
Hard to set the jaw contact point back at the EXACT point point you had before when adjusting it for a different case, then going back to the same cartridge again, but consistency is what we look for and consistency, or perhaps lack thereof, is what it will show you.
Cant see it in the photo I posted, but it actually measures in .0005" increments.
The Lake City 5.56 case below is stamped 08 and for some reason the 9mm case will not touch its shoulder.
And my Hornady cartridge case headspace gauge instructions tells you what adapter to use for specific calibers.
RTFM
Below a Colt 5.56 Field gauge at 1.4736
The field gauge in my adjusted Hornady gauge
And a fired case from my AR15 reading very close to actual chamber headspace minus brass spring back.
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Got this when I first started reloading several years ago. Figured one tool for all calibers/cartridges without having to deal with inserts and trying to measure with calipers .etc.... Quick and easy. Takes a few seconds to check cases after FL sizing to ensure each case shoulder is bumped .0015.
From 2011:
http://forum.accurateshooter.com/threads/larry-willis-headspace-tool.3757422/
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That's a nice tool, but does it measure at the .200" line. Just another spot to be sure of resizing F/L for a nice bolt close and lift.
No. FL sizing dies are based on fired cases from each of my chambers. I also double check FL sized cases to ensure they chamber for a nice bolt close/lift.
Guess I got lucky with 3 relatively cheap Sinclair comparators..Left is BRA, centre is straight BR and right is 284, marked them up then ran comparator over them and to my surprise appears to be making virtually full contact at what looks like to be the same angles...I’ve never had any issues measuring bump but thought I’d check anyhow.
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